1. Field of Invention
This invention relates to trailer hitches and more specifically to a coupling mechanism on a gooseneck trailer hitch of the ball type.
2. Description of the Prior Art
A typical gooseneck trailer hitch is made up of an L shaped structure with a socket or cavity at the bottom end of the vertical portion of the L shaped structure. The socket or cavity is generally formed in a coupler foot plate that attaches to a round or square vertical steel tube or post, such that the foot plate receives the trailer hitch ball mounted on the vehicle which is to tow the trailer. The vertical tube is rigidly and permanently affixed to the horizontal portion of the L shaped structure, which in turn is attached to the front of the trailer.
The coupler at the lower end of the post generally connects with a receiving device, such as a ball, on a pull vehicle. The gooseneck trailer coupler itself is made up various configurations to secure the coupler to the ball. Many gooseneck trailer couplers include front and rear facing portions, one portion usually including a lever that operates to xe2x80x9clockxe2x80x9d and xe2x80x9cunlockxe2x80x9d the coupler. The coupler lever is generally made up of a cylindrical bar having a vertical component which penetrates an aperture in the foot plate and/or a locking plate of the coupler and a horizontal component at its upper end by which the user may grasp the lever. Alternatively, the securing mechanism might consist of a horizontal pin that slides through the vertical post adjacent the foot plate.
With a lever thus described, to couple a gooseneck trailer to a pull vehicle requires manipulation of the coupler lever. Manipulation is usually performed by initially raising the coupler lever vertically so that vertical component is removed from the aperture in the foot plate, thereby allowing the securing mechanism to be positioned to either accept or release the receiving device of the pull vehicle (xe2x80x9copenxe2x80x9d or xe2x80x9cunlockxe2x80x9d position). After the socket has received the receiving device on the pull vehicle, the coupler lever is released, whereupon the vertical component again is received by the foot plate aperture, thereby returning the coupler lever to its original resting position (xe2x80x9cclosedxe2x80x9d or xe2x80x9clockedxe2x80x9d position).
U.S. Pat. No. 5,683,094 is illustrative of a gooseneck coupler mechanism incorporating a coupler lever as described above. As shown therein, the locking mechanism for the device consists of a vertically actuable coupler lever that is urged against an apertured locking plate. In order to release or secure the coupler mechanism, the coupler lever is pulled upward to allow the aperture of the locking plate to be moved into or out of alignment with the receiving device or ball. Once the locking plate is properly positioned, the coupler lever is released to secure the locking plate in the desired position.
U.S. Pat. No. 4,168,847 illustrates a horizontal pin type locking mechanism as referenced above. Specifically, a socket or cavity is illustrated at one end of the vertical post, the socket disposed to receive the towing ball on the vehicle for coupling and uncoupling. A horizontal retainer pin is provided extending along the inner edge of the cavity. The pin is not in place during coupling or uncoupling, but can be inserted in the coupling member once the ball is in the cavity. The ball diameter is such that it cannot move out of the cavity with the pin in place, thereby firmly securing the hitch together.
Another type of mechanism to secure the coupler to a ball is illustrated in U.S. Pat. No. 5,385,363, where there is shown an apertured foot plate pivotally attached to an apertured locking plate such that the apertures of the two plates can align when so desired. An exposed, external spring is used to urge the apertures of the two plates out of alignment under xe2x80x9crestxe2x80x9d conditions. Under the force of the ball passing through the misaligned apertures of the two plates and against the force of the spring, the two plates pivot relative to one another until the apertures are sufficiently aligned to permit the ball to pass there through. Once the ball has passed through the plates, the spring urges the two apertures out of alignment once again, such that the misaligned plates secure around the lower portion or neck of the ball. A vertical retaining pin, similar to the coupler lever described above, may then be used to xe2x80x9clockxe2x80x9d the plates in the rest position so that the ball cannot pull back through.
One drawback to a coupler mechanism such as is illustrated in the ""363 patent is that the spring mechanism used to urge the two plates out of alignment is externally attached to the plates that is necessitated by the manner in which the hitch is fabricated. In the ""363 patent, the foot plate includes a bridge portion that extends around the locking plate. The spring is then externally mounted on the bridge portion and attaches on an external portion of the locking plate utilizing externally mounted eyelets. In any event, being exposed and unprotected, the spring may be easily damage or otherwise interfered with.
Another drawback to gooseneck trailer hitches of the prior art is the current method of manufacture, as is illustrated by the ""363 patent and the ""094 patent. As can be seen in these prior art patents, existing hitches are typically fabricated utilizing hot rolled sheet metal that is cut into the various components of the hitch. To permit sheet metal tooling such as sheering, bending, and machining, the sheet metal is typically low in carbon content, such as 1012 or 1015 low-carbon steel. During the formation process, the sheet metal is commonly stretch formed around a die to created the desired hitch components. While the steel already is lower in strength due to the lower carbon content, such forming processes can weaken the steel even further, shorten the fatigue life and render the components susceptible to stress induced fatigue. For example, in the ""363 patent, the dome of the hitch that overlays the apertured plates is stretch formed by pressing a flat portion of sheet metal around a ball-shaped die. Those skilled in the art will recognize that the resulting circumference and shape of the dome is developed entirely at the expense of sheet thickness and strain distribution at the top of the dome. Yet since the dome rests against the ball, the dome is the portion of the hitch that typically endures the most strain under normal operating circumstances. For this reason, failure of many of the prior art hitches begins to first occur in the dome, which, as shown above, is accelerated by the fabrication manner of the domes of the prior art coupler mechanisms.
It is also difficult to manufacture intricate components or component features in the prior art coupler mechanisms using the hitch fabrication techniques of the prior art. The nature of forming makes it difficult for the dies and cutting tools to access certain portions of the components, such as internal surfaces or small recesses and the like, to form such features. Thus, such components are typically limited to features, whatever their purpose, that can be created on the outer exposed surface of a component.
In any event, once the various components are created, they are typically welded together as shown in the ""094 patent. Welding has several drawbacks, such as for example, bad welds can yield a product that is inherently xe2x80x9cweakxe2x80x9d along the weld points, welding is typically more costly than an a product that is fabricated without welding, welding is more subject to human error and discretion and welding is generally requires more resources and a longer time for fabrication and assembly.
Finally, the fabrication method of cutting and welding as described above is inherently imprecise. Bending is difficult to replicate to tight tolerances and alignment of various components for welding is subject to the relative placement of the parts by the welder. In addition, the dies used in cutting and forming the steel are subject to wear. All of these factors can result in part dimensions that can vary as much as xc2x15 inches.
In light of the foregoing, it would therefore be desirable to provide a gooseneck trailer mechanism that better protects the spring or other components utilized to secure the mechanism in the desired engagement position. Such a hitch would be manufactured to have much tighter tolerances than the devices of the prior art and would be much more durable than the prior art devices. In addition, such a hitch should still be easily and quickly manufactured, while permitting various features to be formed on portions of the hitch that are not accessible by machining equipment.
The present invention provides a gooseneck trailer hitch that incorporates an engagement mechanism spring seated within a protective enclosure. Defined within the protective enclosure is a spring seat that is integrally formed therein for receiving the spring. More specifically, the hitch includes a base plate, a top plate pivotally attached to the base plate, an engagement spring for urging the base plate and the top plate into a trailer ball securing relationship, and a locking handle for locking the base plate and the top plate into a securing relationship relative to one another. The mechanism is essentially comprised of two elements, namely the base plate and the top plate with the features for each element integrally formed therewith. Specifically, these two elements are formed by investment casting thereby permitting various features to be molded into the piece at the time of creation. In the preferred embodiment, a nipple for securing the spring to the top plate is formed on the top plate shoulder that extends into a spring enclosure formed on the base plate. Likewise, a spring seat or pocket is formed within the spring enclosure for receiving and securing the spring to the base plate. A ball seat may also be cast into the surface of the base plate to enhance seating of the hitch on a ball. Because the hitch is formed of two basic components that have all of the necessary elements integrally cast into the components, the hitch requires no welding of various components of the of the base plate or top plate to complete assembly yet still is provided with internally formed features such as the nipples and spring seat. In addition, the hitch can be formed of higher carbon steel than the prior art because the material utilized in formation of the base plate and top plate need not be malleable for the bending and stretch forming that characterizes the fabrication processes of the prior art. Thus, by utilizing investment casting, the hardness of the hitch and strength of the components can be increased. Finally, the hitch can be specifically manufactured to place additional material in those portions of the hitch that are likely to experience the highest loads, such as the hitch dome.